An intake apparatus of an internal combustion engine, which includes two intake valves per cylinder, has been known in the related art (e.g., see Japanese Patent No. 4485541 (hereinafter referred to as “Reference 1”).
Reference 1 discloses an intake manifold connected to an internal combustion engine (an intake apparatus of an internal combustion engine), which includes a pair of (two) intake valves in each cylinder. In the intake manifold disclosed in Reference 1, an intake flow control valve, which controls the flow of intake air, is installed in an intake passage so as to open or close the intake passage. In addition, the intake flow control valve includes a rotating shaft that is installed at the lower end of a flat plate-like valve body (the upstream end of intake air), which includes a flat blade surface, and is accommodated in a recess formed in the lower inner surface of the intake passage when the valve is opened. In addition, when the valve body is rotated to the closing side so as to obliquely rise from the recess, the downstream side tip end of the valve body reduces the cross section of the intake passage, which causes a downstream intake air flow to be deflected such that a tumble flow (a longitudinal vortex) is generated within the cylinder. In addition, one intake passage diverges into two intake passages at a portion of a downstream side head port (i.e., a portion of an intake port inside a cylinder head) downstream of the intake flow control valve, and then communicates with the inside of the cylinder through the intake ports, which are opened or closed by the intake valves, respectively.
In the intake manifold of Reference 1, it is considered that a certain degree of tumble flow may be generated inside the cylinder because the valve body having a flat plate shape is rotated to the closing side so that the downstream side tip end thereof reduces the cross section of the intake passage. However, in the case where one intake passage diverges into two intake passages at a portion of the head port (i.e., a portion of the intake port inside the cylinder head) downstream of the intake flow control valve, it is considered that the stream line of the deflected intake air flow may be hard to form a shape that is capable of generating a strong tumble flow within the cylinder due to the shape of the inner surface of the diverging portion and the intake port downstream of the diverging portion. Therefore, the internal combustion engine, which is provided with a head port (i.e. the intake port) including two intake valves per cylinder has a problem in that it cannot obtain a sufficient strength of the tumble flow generated within the cylinder.
Therefore, a demand exists for an intake apparatus of an internal combustion engine and an intake flow control valve, which do not have the above-described disadvantages.